Hydropower, with 53% (5.3%) of whole power capacity nationwide(Santa catchment) the energy pillar of Peru’s economy, might also beheavily affected by diminishing water resources. The Cañon del Patocentral in the lower Santa river requires a minimum water dischargeof 72 m³/s at full capacity (263 MW). High runoff seasonality and thecurrent water resources decrease and increase of discharge variabilitycontain a strong conflict potential with high economic and socialimpacts (cf. Vergara et al., 2007). Peru’s energy demand is increasingby 7.5%/year (MINEM, 2013). Present and future hydropowerblschemes will need to take into account a lower river discharge.

As virtual water towers, glaciers have been a crucial source for Andean societies and livelihoods. Peru’s mainly remote living population in theCentral Andes has to cope with a strong seasonal variation of precipitations and river runoff interannually superimposed by ENSO impacts.Consequently, direct glacier and lake water runoff constitute a vital continuous water supply and represent a regulating buffer mitigating humanvulnerability to climatic-hydrological variability. This natural system is likely to deteriorate, triggered by accelerated glacier retreat and climaticchanges. This nourishes concerns about a sustainable water supply in the Cordillera Blanca (CB) area and even more so in the arid coastalreaches of the lower Santa watershed while Ancash’s population, irrigation-intense agriculture and hydropower demand increase.Here we present a comprehensive review of the actual situation and perspectives for water resources management in the Peruvian Andes.

Impacts in water supply: accelerated glacier retreat

PRESENT AND FUTURE WATER RESOURCES SUPPLY AND DEMAND IN THE CENTRAL ANDES A COMPREHENSIVE REVIEW WITH FOCUS ON THE CORDILLERA BLANCA, PERU

Introduction

Agriculture accounts for 80% of the total water consumed in Peru.ChaViMoChic, an emblematic project situated on the dry Pacific coast

Increasing water demand: agriculture

References:

ANA (2010): Inventario de Glaciares – Cordillera Blanca. – Unidad de Glaciología y RecursosHídricos (UGRH, Huaraz), 81 pp., Autoridad Nacional del Agua, Lima.

Baraer, M., Mark, B. G., McKenzie, J. M., Condom, T., Bury, J., Huh, K.-I., Portocarrero, C., Gómez,J. & S. Rathay (2012): Glacier recession and water resources in Peru’s Cordillera Blanca. –Journal of Glaciology, 58 (207), pp. 134-150.

Bury, J., Mark, B. G., Carey, M., Young, K. R., McKenzie, J. M., Baraer, M., French, A. & M. H. Polk(2013): New Geographies of Water and Climate change in Peru: Coupled Natural and SocialTransformations in the Santa River Watershed. – Annals of the Association of AmericanGeographers, 103 (2), pp. 363-374.

Carey, M., Baraer, M., Mark, B. G., French, A., Bury, J., Young, K. R. & J. M. McKenzie (2013):Toward hydro-social modeling: Merging human variables and the social sciences with climate-glacier runoff models (Santa River, Peru). – Journal of Hydrology, in press.

Mark, B.G., McKenzie, J.M. & J. Gómez (2005): Hydrochemical evaluation of changing glaciermeltwater contribution to stream discharge: Callejon de Huaylas, Peru. - Hydrological SciencesJournal, 50 (6), pp. 975–987.

MINEM (2013): Avance estadístico del subsector eléctrico: Cifras en octubre 2013. – Ministryof Energy and Mining, Peru.

Rabatel, A., Francou, B., Soruco, A., Gomez, J., Cáceres, B., Ceballos, J. L., Basantes, L., Vuille, M.,Sicart, J.-E., Huggel, C., Scheel, M., Lejeune, Y., Arnaud, Y., Collet2, M., Condom, T., Consoli, G.,Favier, V., Jomelli, V., Galarraga, R., Ginot, P., Maisincho, L., Mendoza, J., Ménégoz, M., Ramirez,E., Ribstein, P., Suarez, W., Villacis, M. & P. Wagnon (2013): Current state of glaciers in thetropical Andes: a multi-century perspective on glacier evolution and climate change. – TheCryosphere, 7, pp. 81-102, European Geosciences Union.

Vergara, W., Deeb, A. M., Valencia, A. M., Bradley, R. S., Francou, B., Zarzar, A., Grünwaldt, A. &S. M. Haeussling (2007): Economic Impacts of Rapid Glacier Retreat in the Andes. – EOSTansactions, American Geophysical Union, pp. 261-268.

Vuille, M., Kaser, G. & I. Juen (2008): Glacier mass balance variability in the Cordillera Blanca,Peru and its relationship with climate and the large-scale circulation. – Global and PlanetaryChange, 62 (1-2), pp. 14-28.

Contact: Fabian Drenkhan fabian.drenkhan@geo.uzh.ch

With 459 km2 glacier area at present the CB (Figure 1) represents thelargest glacierized mountain range of the tropics worldwide. Especiallyas of the second half of the 1970s, it has been strongly affected byblabla

Conclusions

The CB area and Santa basin have raised considerablescientific interest but still represent an in-situ hydro-climatic and glacier data scarce region. Climate changeimpacts are already altering natural water supply whilehuman water demand with needs for a year-roundconstant minimum discharge is increasing.

More comprehensive studies are imperative in order toquantify and capture the complexity and links betweennatural water supply and different water users. The useof bias-corrected satellite data is imperative in order toclose data gaps in the remote and poorly gauged CBarea. More transdisciplinary efforts considering physicaland social key variables must be made to developadaptation strategies to a rapidly changing waterbalance in the Santa basin.

Acknowledgements

This study is part of the “Proyecto Glaciares” funded by the Swiss Agency for Development andCooperation (SDC).

Fabian Drenkhan1, Christian Huggel1, Mark Carey2, Adam French3 & Luzmila Dávila4

1Geography Department, University of Zurich, Switzerland 2Robert D. Clark Honors College, University of Oregon, Eugene, USA3Energy and Resources Group, University of California, Berkeley, USA 4Glaciology and Water Resources Unit, National Water Authority, Huaraz, Peru

Figure 1: Overview of the Santa basin and river with its main features in Peru (red rectangle defines dimensions of upper right detailedmap). Sources used: DEM (USGS SRTM v.3, 2013); National Topographic Map of Peru (Peruvian Ministry of Education, 2010)

Phase 1 Phase 2 Phase 3 Phase 4

D i

s c

h a

r g

e

T i m e

Figure 3: Discharge impact phases of 9 subcatchments in the Santa river (after Bury et al., 2013).

This constant water supply for human consumption especially duringthe months of less precipitation is already decreasing. First evidencescorroborate a passed ‘peak water’ in 6 glacierized subcatchments ofthe Santa river (Figure 3) from where on prior enhanced river runoffwill decrease and level out towards a new still unknown minimumwith higher discharge variability. This contradicts the generalconsensus of a subsequent future discharge decline within a fewdecades. Future annual water stream (Figure 3, Phase 4) will be muchlower than today with a dry season discharge decrease of up to 30%(Baraer et al., 2012; Bury et al., 2013)).

First evidences of a crossed ‘peak water’

Main characteristics of the Santa river basin The 12,200 km² wide Santa basin receives about 675 mm/yearprecipitation (34 station average), characterized by high seasonality.Consequently, river flow has a high-level runoff in the wet season(November-April: ~206 m³/s) and low-level runoff in the dry season(May-October: ~62 m³/s). Glacial melt water contributes with 10-20%in the wet and up to 40% in the dry season (Mark et al., 2005).

massive ice loss witharound 34% glacierarea decline from 1970to 2010 (ANA, 2010;Rabatel et al., 2013;Figure 2). Morefrequent ENSO eventsin the last decades andthe abrupt Pacificclimate shift with ablbl

Figure 2: Glacier area retreat in the CB area.

positive PDO phase and higher SST since 1976 could explain thisaccelerated retreat (Rabatel et al., 2013; Vuille et al., 2008). (Santa effluent), is host to

74,000 ha export cropsincluding 60,000 jobs.Recent expansion efforts(Phase III, Figure 1) standin stark contrast and willeven trigger the decliningriver runoff especiallyduring dry season(cf. Carey et al., 2013).Picture from: http://glaciers.uoregon.edu/Updates.html

River discharge increasedriven by climate-induced glacier melt

Slowdown of dischargeincrease (acceleratedglacier retreat) reachingthe peak water

Pronounced decrease ofdischarge and increaseof discharge variability

Discharge levels out until towards a new minimum(negligible influence of retreated glacier bodies) withhigh annual discharge variability

Increasing water use: new hydropower schemes

PROYECTO GLACIARES

Data from UGRH (ANA, 2010)

Data 1990: Georges, 2004Data 1987, 1996: Silverio & Jaquet, 2005